Method for the production of titanium



Nov. 18," 1952 J. GLASSER ET AL METHOD FOR THE PRODUCTION OF TITANIUMFiled May 2, 1949 /a @maga/fz I H Ml@ fl; MZK

fnl/E17 227275 Patented Nov. 18, 1952 METHOD FOR THE PRODUCTION FTITANIUM Julian Glasser, LaI Grange, and Clifford! A. Hampel, Homewood,Ill., assignors, by mesne assignments, to Kennecott Copper Corporation,

New York, N. Y.

Application May 2, 1949, Serial No. 90,954

(Cl. 'I5-84) 4 Claims.

'I'he present invention relates to a method for producing pure ductiletitanium in coarse crystalline form, or titanium invsponge or powderform.

The unusually desirable physical properties oi pure ductile titanium,such as its high strength, light weight and high corrosion resistance,make the metal ideal as a structural material. However, the metal hasnot come into important industrial use, due to the high cost ofextracting or recovering the metal from its ores. themselves areplentiful and inexpensive, but conventional ore-reducing practices areof no avail in extracting the highly active titanium metal. Y

There are several known methods for preparing `pure, ductile titaniummetal. In all of these known methods, the essential reaction is thatbetween a, titanium compound 'and metal such as sodium, potassium. ormagnesium. Thus, Hunter (JACS, vol. 32, 1910) heated a mixture oi highlypuried titanium tetrachloride and sodium in a steel bomb capable ofwithstanding an internal pressure of 80,000 pounds. The resultingproduct was leached with water, resulting in the formation of a graypowder mixed with small rounded grains of titanium. The Hunter method isstill used in laboratory preparations oi titanium, but it is evidentthat the process is not feasible on a commercial scale. y

The reduction of the titanium compounds by means of reactive metals ofthe type indicated is handicapped by the cost of the operations becauseofthe high power requirements. the necessity of providing pure reducingmetals, and the dimculty in handling the reducing agents.

The ores Further, the purity of the titanium metal thus produced hasbeen limited by the processes used for separation of the reactionmixture, due to the extreme ainity of titanium metal for oxygen,nitrogen. and other common gases. Leaching the reaction product has thedisadvantage that the titanium metal reacts with the water to liberatehydrogen and to form oxygen derivatives of titanium. i

It has also been suggested to decompose gaseous titanium tetraiodide ona hot filament or surface. This method is usually considered apurication step rather than a means for the production of elementaltitanium, inasmuch as the iodide is normally prepared by the reaction ofiodine with titanium metal Although the iodide process is capable ofproducing a very high purity titanium, the cost of rst obtaining thepure iodide is very high and the vacuum equipment and high temperaturesrequired limit the quantity which can be prepared in a batch." j Anobject of the present invention is to pro-f1' vide an economical methodfor the of pure, ductile, Ielemental titanium.

Another object oi the invention is to provide 'a method for theproduction of titanium without' the necessityv of excessive powerrequirements;

Another object of the present invention is 'to provide a unitary proce sfor the production of titanium from its ores, o; its halogenatedderivaves.

Another object of the present invention is to.. provide, as a part of aunitary process for the. production of titanium, a method oi' growingtitanium crystals large enough to be stable on exposure to air. A

Other and further objects of the invention will be apparent from thefollowing description. In general, the present invention contemplatesproduction the reduction oi a'titanium halide, such as thevtetrachloride, as by means of an alkali metal amalgam, such as a sodiumamalgam, with the recovery of pure elemental titanium from the reactionmixture.

More. particularly, the reducing agent to be.

used in accordance with this invention is a sodium amalgam such as isproduced in types of mercury-chlorine cells that are widely used in thefield of caustic soda manufacture. The chlorine cell consists of anelectrolytic cell in which sodium-mercury amalgam and chlorine areproduced by the electrolysis of a brine solution be; tween a` movingmercury cathode and graphite anodes. The two most prevalent types ofcellsare known as the rocking and stationary types. The chlorine cellalso has the advantage of serving as a source of chlorine-which maybe'used in the chlorination of a titanium ore consisting essentially oftitanium dioxide to convert the latter to the tetrachloride.

Operating conditions in the chlorine cell can` be adjusted to produce asodiu -mercury amal-- gam having a wide range of sodi m content. Sodiumand mercury form solid compounds when the sodium content of the mixtureis above about 0.5%. We prefer to use a sodium amalgam having a, sodiumcontent from about 0.05 to 0.5% by weight. and preferably between 0.15%and 0.25% by weightsodium. The amalgam produced within this range ofsodium concentratie .i is soluble in the liquid mercury. The viscosityof the amalgam solution does not become objectionably high until thesodium concentration is increased to -3' above 0.5% whereupon the sodiumamalgammercury mixture becomes diilicult to handle.

By conducting the reduction of the titanium y -1ide in the presence ofmercury, several adi \tages may be realized. First, the amalgam is muchmore'easily handled and carried into the reaction zone than a purealkali metal. Further, the presence of mercury has been found todeactivate'the titanium metal produced in the reduction reaction,lessening the tendency of the metal to become oxidized. In addition.objectionable impurities. such as water, oxygen, nitrogen, hydrogen andmany metals are not soluble or occluded in mercury or the amalgam andare thus not introduced into the titanium metal during the reductionstep. In addition, heat transfer problems are simplified when an amalgamis used rather than an alkali metal. l

. As the titanium halide, we prefer to usetitanium tetrachloride, eitherin liquid or gaseous phase. This halide may be easily and economically'produced by chlorinating ilmenite, rutile,

titanium oxide slags, pure titanium dioxide. or

range between 100 to 300 F. -The preferred range of temperaturev isbetween 190 to 220 F. The reaction is carried out in the presence ofpureiner-t gases, such as helium, argon, neon, krypton and the like, toprevent contaminating the product with air or other gases. The propor-ftion of sodium (in the amalgam) to the titanium tetrachloride may bevaried over a wide range, but we prefer to .use an excess of sodium overthatl theoretically required to completely reduce the titaniumtetrachloride.

Intimate admixture of titanium tetrachloride and the sodium amalgam isessential in the reaction zone. Mixing of the reactants may beaccomplished by introducing liquid titanium tetrachloride into avigorouslyv stirred pool of sodium amalgam either from above orbelow thesurface of the liquid amalgam. Intimate contact of the reactants canalso be effected by bubbling liquid titanium tetrachloride through aliquid sodium amalgam. Another method of mixing is by runninga jet ofilnely dispersed liquid titanium4 tetrachloride or gaseous titaniumtetrachloride into a A,iet of finely divided liquid sodium amalgam.Since 'the' quantity of sodium amalgam involved will be much more thanthe quantity of titanium tetrachloride, the relative proportions of theingredients entering the reaction zone may be controlled by using theamalgam as a pumping fluid. Through proper arrangement of Jets ornozzles, the amalgam can pump the desired amount of titaniumtetrachloride into the reaction zone in venturi or aspirator fashion. Inaddition, the amalgam may be added directly, with agitation, to a supplyof -titanium tetrachloride in the reactor.

` To facilitate further reaction after initial mixing of the reactants,it is important to keep the reactants agitated in the reaction zone bysuitable mechanical means.

' pressure- The reductionin-the reaction zone is completed in a'shortperiod of time and proceeds smoothly without any violence.

The reaction product is a finely divided black powder that floats on thesurface of mercury or the spent amalgam. Individual particles of thispowder have diameters in the-range of 0.1 to 10 microns. The mercury orspent amalgam may be drained or filtered oil! by any well known gravityseparation means such as by the use of a gold seal type filter. Thespent amalgam, which will normally contain less than about 0.10 sodium,may then be recycled to the cell plant.

oxidizing conditions, and preferably under a vacuum. normally less thanabout` 0.01 mm. pressure and usually on the order of about 0.0001 mm.

Instead of using a vacuum, the furnacing zone may be filled with aninert gas of the type mentioned above, in which case pressures above orbelow atmospheric may be used. The transfer from the reduction zone tothe furnacing system may be effected by gravity, or by a suitable typeconveyor.

The reaction product in the furnacing operation is first subjected to atemperature in the range from about 400 to 700 F. to distill oif theresidual mercury. Normally, the residual mercury4 will be on the orderof about 1% of the mercury introduced into the reduction zone. Duringthe furnacing operation, proper precautions must be taken to prevent thepowder from blowing out of the furnace. This may be accomplished byplacing a screen over the furnace pot to retain the powder at the baseof the furnace.

. After the mercury is distilled oil, the remaining product, containingsodium chloride, titanium metal and any titanium sub-chlorides, isheated in a non-oxidizing atmosphere to temperatures above 1500 F.usually from 1500 to 2000 F. to separate the sodium chloride from themix-ture. At these temperatures, any sub-chlorides of titanium presentin the mixture are decomposed or distilled oilat reduced pressures. Whenperforming the furnacing operation under conditions of about 0.0001 mm.pressure, substantially al1 of the sodium chloride will be distilled ata temperature in the range of about 1800 -to 2000 F. and will condenseon the colder walls of the furnace. Alternatively, some residual sodiumchloride may be retained to be drained or distilled off in-a subsequentmelting operation.

The residue remaining in the furnace after the removal of sodiumchloride consists essentially of pure, ductile titanium crystals. Theindividual crystals are cemented together during the furnacing operationto form agglomerates having crystal sizes much larger than the particlesize resulting from the original reaction The crystals thus produced arestable in air, water. and acids, and may be easily handled forsubsequent melting and alloying operations. It is quite possible thatthe molten sodium chloride present in the separating furnace serves as amatrix for promoting the growth of the crystalline agglomerates.Accordingly, it is sometimes desirable to retain the sodium chloride inthe separating furnace without volatilizing the same, but removing itfrom the metallic titanium by leaching or subsequent melting.

It is to be understood that the growth of titanium crystals from amixture of fine titanium powder and sodium chloride, with or withoutsubchlorides of titanium, is not restricted toY the source of finelydivided metal herein described, but may be used with other processesthat produce a finely divided titanium powder. In addition, other alkalimetal and alkaline earth metal halides, for example, potassium chloride,calcium chloride and magnesium chloride or other halides may be used inplace of sodium chloride, at temperatures above the melting point of therespective halide. Y

'I'he crystals of titanium produced in the furnacing operation may alsobe compressed and sintered into coherent masses.

The crystals recovered from the furnacing operation contain more than99% titanium and are extremely ductile. The purest and most ductilecrystals appear to be the largest. The largest crystals have a Vickershardness in the range from about 95 to 135 and contain more than,

99.9% titanium. This is equivalent to the purest and most ductiletitanium metal prepared by other processes. The crystals themselves maybe cold rolled to about 50% reduction in thickness.

A further description in the process proposed will be made in connectionwith the attached ow diagram, which shows one embodiment of the presentinvention. Y

Relatively large quantities of mercury are introduced into the cellplant which comprises a conventional mercury-chlorine cell. The mercuryleaving the cell plant contains sodium metal in the form of an amalgam,having a sodium content determined by the operating conditions in thecell plant. Preferably, a sodium amalgam containing about 0.2% sodium,and having enough sodium to at least theoretically completely reduce thesubsequently added TiCl4, is introduced into a reactor plant lled withan inert gas of the type described and maintained at a temperaturebetween 100 and 300 F. Into the reactor plant is also introducedtitanium tetrachloride. The reaction mixture leaving the reactor plantcontains the original mercury, sodium chloride, and a powdery reactionproduct which is probably a mixture of titanium metal and titaniumsub-chlorides (TiCh).

The reaction mixture is next passed into a suitable mercury filter ordraining system, where approximately 99% of the mercury is recovered andrecycled to the cell plant as shown. The mixture leaving the mercuryfilter, containing residual mercury, sodium chloride, and the metallictitanium-containing product is next passed to a separating furnace whereabout 80% of the sodium chloride present is vaporized oi or drained oifas a liquid. The sodium chloride recovered from the furnacing operationmay be recycled to the cell plant, together with the rest of the sodiumchloride recovered from the subsequent melting furnace, with theaddition of water to form a brine solution. Any titanium sub-halideswhich are not decomposed in the separating furnace may be removed fordisposal or recycling. Ihe residual mercury, which will normally beabout 1% of the mercury originally present in the reaction mixture, isrecovered from the separating furnace and also recycled to the cellplant in conjunction with mercury recovered from the filteringoperation.

ing furnace operating under vacuum, or in the presence of inert gases,where the remaining sodium chloride is distilled or melted off and thetitanium melted for subsequent casting. It is to be understood that themelting operation may be eliminated, and the titanium crystals resultingfrom the treatment in the separating furnace may'be compacted as inconventional powder metallurgy procedures. In this event, the stabletitanium crystals may be separated from the titanium-sodium` chloridemixture leaving the separating furnace by leaching out the sodiumchloride with water. As discussed hereinabove, the titanium crystalsgrow in the separating furnace to a stable form unaffected by water sothat leaching with water will suiiice to separate the sodium chloridefrom the mixture without any deleterious effect on the titanium metal.

Extended exposure of the crystals to the conditions present in theseparating furnace results in the sheets of titanium metal which may berecovered without the necessity of further melting or powder metallurgyprocesses.

The above flow diagram presents one embodiment of the present invention,but it will be evident that various modifications can be made in theprocess herein disclosed without departing from the spirit of theinvention, and it is not our intention to limit the scope of theinvention other than necessitated by the scope of the appended claims.

We claim as our invention:

1. The method of producing elemental titanium from titaniumtetrachloride, which comprises vigorously mixing titanium tetrachloridewith sodium amalgam in the presence of an inert gas, the sodium contentof said sodium amalgam being suicient theoretically to completely reducesaid titanium tetrachloride to titanium, continuing to vigorouslyagitator the reactants until a reaction mass of elemental titanium,sodium chloride and spent amalgam results, separating the sodiumchloride and spent amalgam from the titanium and recovering elementaltitanium.

2. The method of producing elemental titanium from titaniumtetrachloride,- which comprises vigorously mixing titanium tetrachloridewith sodium amalgam in the presence of an inert gas, the sodium contentof said sodium amalgam being suicient theoretically to completely reducesaid titanium tetrachloride to titanium, continuing to vigorouslyagitate the reactants until a reaction mass of elemental titanium,sodium chloride, sub-chlorides of titanium and spent amalgam results,removing a substantial amount of mercury from said reaction mass,transferring the remaining reaction mass to a, furnacing zone withoutexposure to the air, heating said remaining reaction mass in saidfurnacing zone to distill oi sodium chloride and decompose sub-chloridesof titanium present, and recoveringas the residue in said furnacing zoneductile titanium` crystals.

3. The method of producing elemental titanium from titaniumtetrachloride, which comprises vigorously mixing titanium tetrachloridewith sodium amalgam in the presence of an inert gas. the sodium contentof said sodium amalgam being suiiicient theoretically to completelyreduce said titanium tetrachloride to titanium, continuing to vigorouslyagitate the reactants until a reaction mass of elemental titanium,sodium chloride, sub-chlorides of titanium and spent amalgam results,removing a substantial amount of mercury from said reaction mass,transferring the remaining reaction mass to a fumacing zone withoutexposure to the air, heating said remaining reaction mass in saidfurnacing zone to a temperature of at least 1500 F. under vacuumconditions to separate sodium chloride and decompose sub-chlorides oftitanium present, and recovering as the residue in said {urnacing zoneductile titanium crystals.

4. The method oi producing elemental titanium from titaniumtetrachloride, which comprises vigorously mixing titanium tetrachloridewith sodium amalgam in the presence of an inert gas, the sodium contentof said sodium amalgam being suillcient theoretically to completelyreduce said titanium tetrachloride to titanium, continuing to vigorouslyagitate the reactants until a reaction mass of elemental titanium,sodium chloride, sub-chlorides of titanium and spent amalgam results,removing a substantial amount of mercury from said reaction mass.transferring the remaining reaction mass to a iurnacing zone withoutexposure to the air, heating said remaining reaction mass in saidfurnacing zone to a temperature of between about 1500 and 2000v F.

. in a non-oxidizing atmosphere to remove at least a portion of thesodium chloride and decompose sub-chlorides of titanium present. andfurther 8 heating the remaining mixture containing titanium and residualsodium ,chloride to a sumciently high temperature -to voiatilize saidresidual sodium chloride and to melt said titanium.

JULIAN GLASSER.. CLIFFORD A. HAMPEL.

REFERENCES CITED The following references arey of record in the ille ofthis patent: f

UNITED STATES PATENTS Number Name Date 2,148,345 Freudenberg Feb. 2i,1939 2,205,854 Kroll June 25, 1940 2,482,127 schlechten et al. Sept. 20,1949 2,564,337 Maddex Aug. 14, 1951 OTHER REFERENCES

1. THE METHOD OF PRODUCING ELEMENT TITANIUM FROM TITANIUM TETRACHLORIDE,WHICH COMPRISES VIGOROUSLY MIXING TITANIUM TETRACHLORIDE WITH SODIUMAMALGAM IN THE PRESENCE OF AN INERT GAS, THE SODIUM CONTENT OF SAIDSODIUM AMALGAM BEING SUFFICEINT THEORETICALLY TO COMPLETELY REDUCE SAIDTITANIUM TETRACHLORIDE TO TITANIUM CONTINUING TO VIGOROUSLY AGITATE THEREACTANTS UNTIL A REACTION MASS OF ELEMENTAL TITANIUM, SODIUM CHLORIDEAND SPENT AMALGAM RESULTS, SEPARATING